Measuring Assembly

The invention relates to a measuring assembly for determining a property of a multiphase, flowable medium.

It is possible, by means of microwaves, to determine the physical quantities of permittivity and loss factor of a medium in a process line. From these two variables—measured either at one or over many different frequencies—it is possible to draw conclusions regarding application-specific parameters, for example the proportion of water in a mixture of water and other non-polar or weakly polar components or a solid content in a liquid medium.

The established transmission/reflection measurement is described in L. F. Chen, C. K. Ong, C. P. Neo, V. V. Varadan, V. K. Varadan—“Microwave Electronics, Measurement and Materials Characterization,” John Wiley & Sons Ltd., 2004. For this purpose, the microwave signal interfaces at two different positions at the medium in a container or measuring tube, the scatter parameters (transmission and optionally reflection) are measured between these interface structures, and the mentioned physical properties of the medium are calculated from the measured scatter parameters.

WO 2018 121927 A1 teaches a measuring assembly for analyzing properties of a flowing medium by means of microwaves. In addition to the microwave antennas, the measuring assembly has an electrically insulating lining layer on the inner peripheral surface of the measuring tube. This lining layer forms a dielectric waveguide via which at least part of the one microwave signal can travel from a first microwave antenna to a second microwave antenna. One application for such a measuring assembly is the determination of the proportions of solids in the liquid medium being conveyed. WO 2021/099152 A1 teaches a microwave antenna which has a front section in contact with the medium, via which the excitation signal is emitted into the medium. A disadvantage of the disclosed solutions is that they are not suitable for hygiene applications in the disclosed form.

The object of the invention is to remedy this problem.

1 The measuring assembly according to the invention for determining a property of a multi-phase, flowable medium comprises: preferably a metal measuring tube for carrying the medium, wherein the measuring tube has a first antenna receptacle, a first microwave antenna which is arranged in the first antenna receptacle, a first separating disc for separating the first microwave antenna from the medium, wherein the first separating disc is arranged in the first antenna receptacle, wherein the first microwave antenna is arranged behind the first separating disc in the radial direction, a measuring circuit, wherein the measurement circuit has a high-frequency generator for supplying the first microwave antenna with an excitation signal, in particular with a sequence of high-frequency signals, wherein the measurement circuit is configured to determine the property of the medium on the basis of a received measurement signal. The object is achieved by the measuring assembly according to claim.

The advantage of the measuring assembly according to the invention is that measuring assemblies for wastewater or pulp-and-paper applications, in which the first microwave antenna is in direct contact with the medium, can be easily converted for hygiene applications. This is achieved by means of the first separating disc which is arranged between the medium to be guided and the first microwave antenna and accordingly prevents the first microwave antenna from coming into contact with the medium. The first separating disc can be designed in such a way that it meets the application-related hygiene requirements. For this purpose, a special material with which the medium may come into contact or a special geometry in which undercuts are avoided can be provided. It is also advantageous that with a suitable choice of material and geometry of the first separating disc, improved irradiation of the excitation signal into the medium is achieved.

Within the meaning of the invention, the separating disc is to be understood as a disc. A disc is a geometric body which, at least partially, assumes the shape of a cylinder and whose disc radius is, at least partially, many times higher than its thickness. The separating disc cannot therefore be understood as part of a liner applied to the inside of the measuring tube within the meaning of WO 2018/121927 A1, as a waveguide within the meaning of U.S. Pat. No. 4,755,743, as part of an electrically insulating measuring tube body within the meaning of U.S. Pat. No. 3,999,443 or as an electrically insulating sheath within the meaning of WO 00/43759 A1.

The high-frequency generator is preferably configured to generate an excitation signal which covers a frequency range from 100 MHz to 100 GHz, in particular from 500 MHz to 50 GHz and preferably from 800 MHz to 15 GHz. The first microwave antenna is designed to radiate the provided excitation signal into the interior of the measuring tube or into the medium. The excitation signal is a microwave signal which is substantially free from the influence of the medium in the measuring tube. The first microwave antenna can also detect the reflected back-propagating measurement signal. The measurement signal is also a microwave signal which substantially comprises the excitation signal with a component resulting from the interaction of the excitation signal with the medium. The measurement circuit has a microcontroller, logic switching elements and/or electrical components and is designed to determine a property of the medium depending on the proportion.

One embodiment provides that the first separating disc comprises a material which is listed in the following list: polyetheretherketones (PEEK) polytetrafluoroethylene (PTFE) perfluoroalkoxy (PFA) glass ceramic Advantageous embodiments of the invention are the subject-matter of the dependent claims.

One embodiment provides that the first separating disc has a first separating disc receptacle in which the first microwave antenna is arranged, in particular fused. In terms of hygienic design, the material must meet the applicable standards and guidelines for contact with food required in the application such as applicable parts of the US FDA (2022). The material preferably meets the requirements of FDA (2022), EHEDG, in particular EN 1672-2 and/or DIN EN ISO 14159:2008-07, 3-A Sanitary Standards, (EC) No. 1935/2004, (EU) No. 10/2011, GB 4806.1-2016, GB 4806.7-2016 and/or GB 4806.11-2016.

1 One embodiment provides that the first separating disc has a first separating disc section with a first separating disc thickness d, 2 wherein the first separating disc has a second separating disc section with a second separating disc thickness d, 1 2 wherein the first separating disc thickness dis smaller than the second separating disc thickness d, wherein the first separating disc section forms a minimum separation between the medium and the first microwave antenna. The advantage of a fused connection between the first microwave antenna and the first separating disc receptacle or the first separating disc is the improved coupling of the generated excitation signal into the separating disc.

1 One embodiment provides that the first separating disc thickness dis a maximum of 1 millimeter, in particular a maximum of 1.5 millimeters and preferably a maximum of 2 millimeters. It is advantageous if the distance between the first microwave antenna and the medium is as small as possible. The first separating disc has several separating disc thicknesses to improve the connection of the first microwave antenna to the first separating disc itself and to achieve the most optimum mechanical stability of the first separating disc. This allows the first section of the separating disc through which the excitation signal propagates to be made as thin as possible. For the second separating disc section—through which a much smaller amount of the excitation signal propagates—a comparatively high separating disc thickness can be provided to improve the mechanical stability of the first separating disc.

1 1 1 One embodiment provides that the measuring tube has a measuring tube collar extending around a circumference of the first antenna receptacle. It has been found that the portion of the excitation signal radiated into the medium that is useful for the measurements (the reflection factor is below −6 dB, i.e. at least 75% of the power is radiated) decreases with increasing thickness of the separating disc. For the claimed measuring assembly it could be demonstrated that with a separating disc thickness dof 1 millimeter approximately 90% of the useful band (1.8-3 GHz), with a separating disc thickness dof 2 millimeters only about 75% of the usable band and with a separating disc thickness dof 3 millimeters, only about 50% of the useful band is below −6 dB. This means that in the latter case. only half of the useful band contributes to determining the properties of the multiphase, flowable medium.

The measuring tube collar has the advantage that it increases the mechanical stability of the first antenna receptacle and therefore also the robustness of the entire measuring assembly, in particular the module comprising the first microwave antenna, the first separating disc and any other components.

1 2 wherein the measuring tube has a second measuring tube section with a second outer diameter D, 1 2 wherein the first outer diameter Dis larger than the second outer diameter D, wherein the first antenna receptacle is located in the first measuring tube section. One embodiment provides that the measuring tube has a measuring section in which the first microwave antenna is arranged, wherein the measuring tube is spherical in the measuring section. One embodiment provides that the measuring tube has a first measuring tube section with a first outer diameter D,

One embodiment comprises: a first disc holder for fixing the first separating disc in the first antenna receptacle, wherein the first disc holder is designed and arranged on the measuring tube in such a way that the first separating disc is clamped in the first antenna receptacle. One embodiment provides that the first separating disc has, in a front section, a sealing agent receptacle running along the circumference, in particular in the form of an indentation, with a sealing agent arranged therein. The advantage of the embodiment is that a circular first antenna receptacle can be realized in the measuring tube for an at least partially cylindrical separating disc without undercuts forming between the measuring tube and the first separating disc in which solids of the medium can accumulate. By arranging the first separating discs flush with the front of the measuring tube, no steps are formed in the medium-carrying measuring tube channel and therefore no source of turbulence in the medium.

One embodiment provides that the first microwave antenna has a metallic carrier body with a carrier body receptacle, wherein the first microwave antenna has a ceramic with a metallization, which is arranged in the carrier body receptacle, wherein the first microwave antenna has an opening extending through the carrier body and the ceramic, wherein the first microwave antenna comprises a coaxial connector that is arranged in the opening. The sealing means can be a sealing means in a solid state during assembly (e.g. an O-ring) or a sealing means initially applied in liquid form and then hardened.

One embodiment comprises: a first disc fastener which is designed to fix the first separating disc to the disc holder and/or the first microwave antenna and to shield the first microwave antenna. The advantage of the design is the high compactness of the first microwave antenna with high pressure and temperature resistance. Such a first microwave antenna is known from WO 2021/099152 A1, to which reference is made in its entirety.

One embodiment provides that the first disc fastener and the first disc holder are designed and arranged around the first microwave antenna in such a way that a ground connection to the metallization (i.e. a connection to ground via the metallization) is realized. The first disc fastener lies on the back of the first microwave antenna. The advantage of this is that the signal loss of the excitation signal is reduced by preventing a portion of the excitation signal from being emitted via the rear side. It is further advantageous if the first disc fastener additionally or alternatively covers or shields a lateral surface of the first microwave antenna.

One embodiment comprises: a second microwave antenna, in particular structurally identical to the first microwave antenna, wherein the measuring tube has a second antenna receptacle, in particular diametrically oriented to the first antenna receptacle, wherein the second microwave antenna is arranged in the second antenna receptacle, a second separating disc for separating the second microwave antenna from the medium, wherein the second separating disc is arranged in the second antenna receptacle, wherein the second microwave antenna is arranged behind the second separating disc in a radial direction, wherein the second microwave antenna is designed to receive the microwave signal. One embodiment comprises: a second disc holder for fixing the second separating disc in the second antenna receptacle, wherein the second disc holder is designed and arranged on the measuring tube in such a way that the second separating disc is clamped in the second antenna receptacle. One embodiment provides that the measuring tube has a measuring tube interior, wherein the first disc holder is connected to the second disc holder via at least one fastening means, wherein the first disc holder and the second disc holder is arranged on the measuring tube and connected to one another in such a way that they cause a force in the direction of the measuring tube interiors on the respective disc holder. The metallization of the disc holder prevents the microwave signal (excitation signal) from partially radiating into the electronics chamber instead of into the medium.

1 FIG. 1 7 5 7 5 7 7 10 10 5 5 10 5 5 21 7 21 7 21 5 5 5 7 21 28 28 5 5 28 21 5 5 28 21 7 19 shows an exploded view of a module of a first embodiment of the measuring assemblyaccording to the invention. The depicted module comprises a first separating discwhich is designed to separate the first microwave antennafrom the flowable medium. The first separating discis intended to prevent the first microwave antennafrom coming into contact with the flowing medium. The first separating discis designed to meet the requirements of FDA, (EC) No. 1935/2004, GB 4806.1-2016, GB 4806.7-2016 and/or GB 4806.11-2016. Furthermore, the first separating dischas a first separating disc receptaclewhich can be designed as a recess. For this purpose, it preferably has or is made of PEEK, PTFE, PFA, glass or ceramic as material. The first separating disc receptacleis designed in such a way that a first microwave antennacan be arranged at least partially therein. For sufficient fastening, a material-to-fused fastening of the first microwave antennain the first separating disc receptaclecan be provided. The first microwave antennais designed to transmit an excitation signal into the medium. Furthermore, the first microwave antennahas a metallization on an outer lateral surface. The module further comprises a first disc holderwhich is designed to fasten the first separating discto a measuring tube. For this purpose, the first disc holderis designed and can be arranged on the measuring tube in such a way that the first separating discis clamped in the first antenna receptacle (not shown) provided in the measuring tube. The first window holderhas an opening through which the first microwave antennacan be arranged or through which the first microwave antennaextends in the mounted state. The first microwave antennais attached to the first separating discand the first disc holderby a first disc fastener. The first disc fastenernot only serves to fasten the first microwave antenna, but must also be designed and arranged in such a way that it shields the first microwave antennain the radial direction. For this purpose, the first disc fastenerand the disc holderare designed and arranged around the first microwave antennain such a way that a ground connection to the metallization of the first microwave antennais realized. The first disc fasteneris mechanically connected to the first disc holderand the first separating discby means of at least one fastening means(e.g. screws or rivets).

8 11 6 22 29 When using two microwave antennas, it is advantageous to use two structurally identical microwave antennas. In this case, one of the two microwave antennas is configured to transmit the excitation signal, and the correspondingly other microwave antenna is designed to receive a measurement signal. Accordingly, the module then comprises a second separating discwith a second separating disc receptacle, a second microwave antenna, a second disc holderand a second disc fastener.

2 FIG. 1 FIG. 1 1 2 3 4 25 24 7 8 25 2 2 3 4 27 26 shows an exploded view of the entire first embodiment of the measuring assemblyaccording to the invention. The shown measuring assemblycomprises two of the modules shown inin an assembled state. These can be arranged diametrically on a measuring tubewith a first antenna receptacleand a second antenna receptacle. For adequate sealing, a sealing meansis provided in each case which can be arranged in an end face sealing means receptacleof the separating discs,. The sealing meanscan be designed like a sealing ring. The measuring tubehas a connection device in the form of a flange on each end face. The measuring tubeis spherical in the region of the antenna receptacles,. The two modules can be mechanically connected to one another via fastening meansin such a way that they are tensioned against one another, and a mutual force is therefore exerted on the modules in the direction of the measuring tube interior.

3 FIG. 1 FIG. 1 3 3 2 7 12 7 13 7 12 5 3 5 5 7 1 2 1 2 1 shows a cross section through a first embodiment of the measuring assembly. In the first antenna receptacle, the mounted module depicted inis arranged in the first antenna receptacleof the measuring tube. The first separating dischas a first separating disc sectionin which the first separating dischas a first separating disc thickness d, and a second separating disc sectionin which the first separating dischas a second separating disc thickness d. The first separating disc thickness dis smaller than the second separating disc thickness d. The first separating disc sectionforms a minimal separation between the medium within the measuring tube interior and the first microwave antenna. The first separating disc thickness dis a maximum of 3 millimeters, in particular a maximum of 2 millimeters and preferably a maximum of 1 millimeter. Given the design of the different separating disc thicknesses, a first antenna receptacleis formed in which the first microwave antennais arranged. The first microwave antennacan be fused to the first separating discby means of an adhesive. For this purpose, an adhesive gap (approx. 0.2 mm) can be provided between the end face of the first microwave antenna and the opposite surface of the first antenna receptacle, which is filled with an adhesive.

7 24 25 24 25 24 25 Furthermore, the first separating dischas a sealing means receptaclein which a sealing meansin the form of a sealing ring is arranged. The sealing means receptacleis designed in such a way and the sealing meansis configured and arranged in the sealing means receptaclein such a way that it is at least partially in contact with the medium and no cavities form. The sealing meansconsists of a material suitable for hygienic applications.

21 7 7 21 22 28 7 21 7 21 21 5 5 21 A metallic first disc holderis arranged in the radial direction behind the first separating discand exerts a force on the first separating discin the direction of the measuring tube interior. The first disc holdercan interact with a second disc holderof a second module that is arranged diametrically. A first disc fasteneris arranged in the radial direction behind the first separating discand the first disc holder, and is designed to connect the first separating discto the first disc holder. In addition, the first disc holderis designed in such a way that it covers as large a rear surface of the first microwave antennaas possible and creates a connection between the metallization of the first microwave antennaand the metallic first disc holder.

5 30 31 32 32 33 34 34 5 34 The first microwave antennahas a metalized carrier bodywith a carrier body receptaclein which a ceramicis arranged. The ceramichas a through openingthrough which a coaxial connectoris inserted. The coaxial connectoris connected to the measurement circuit which has a high-frequency generator for feeding the first microwave antennawith an excitation signal. Alternatively, the coaxial connectorcan be designed to forward an incoming measurement signal to the measurement circuit.

2 15 3 15 The measuring tubehas a measuring tube collarextending around a circumference of the first antenna receptacle, in which the entire module is arranged. The measuring tube collarfacilitates installation and ensures a stable arrangement of the module on the measuring tube.

1 When using two structurally identical microwave antennas or modules, the measuring assemblyhas two of the shown assemblies.

4 FIG. 101 107 125 107 125 125 107 121 121 114 107 121 114 125 107 114 121 105 121 114 110 107 105 110 128 127 128 105 5 shows an exploded view of a module of a second embodiment of the measuring assemblyaccording to the invention. The module comprises a first separating discwhich tapers conically at the end face. A sealing meansin the form of a sealing sleeve to be arranged on the front side of the first separating discalso tapers conically at the end face. The sealing meanshas a first sealing means section in which it is cylindrically designed and has a substantially constant first sealing means diameter. Furthermore, the sealing meanshas a second sealing means section with a second sealing means diameter, which is always smaller than the first sealing means diameter and decreases or increases in the longitudinal direction. The first separating disccan be connected to a measuring tube via a first disc holder. The first disc holderhas a thread for this purpose. A resilient elementis arranged between the first separating discand the first disc holder. In the illustrated embodiment, the resilient elementconsists of a cylindrical leaf spring. The four individual components mentioned—the sealing means, the first separating disc, the elastic elementand the first disc holder—can be assembled together and fastened in a receptacle in the measuring tube. Thereafter, a first microwave antennacan be guided through the first disc holderand the resilient elementand can be arranged in a provided first separating disc receptaclein the first separating disc. For fastening the first microwave antennain the first separating disc receptacle, a first disc fasteneris provided which comprises two clamp-shaped discs. Four fastening meansserve to fasten the module to the measuring tube. Furthermore, the first disc fasteneris designed and arranged behind the first microwave antennain a radial direction in such a way that the largest possible rear surface of the first microwave antennais covered.

108 111 106 122 129 When using two microwave antennas, it is advantageous to use two structurally identical microwave antennas. In this case, one of the two microwave antennas is configured to transmit the excitation signal, and the correspondingly other microwave antenna is designed to receive a measurement signal. Accordingly, the module then comprises a second separating discwith a second separating disc receptacle, a second microwave antenna, a second disc holderand a second disc fastener.

5 FIG. 3 FIG. 2 FIG. 101 101 102 102 2 shows a cross section through a second embodiment of the measuring assembly. The measuring assemblyhas a measuring tubewhich—unlike in—is not designed spherical. Instead, the medium-carrying path in a cross-section in the measuring section has a circular surface which is shortened by two diametrically oriented circular segments. The depicted measuring tubeis a milled part which is machined from a metallic block. However, the measuring tubewith the spherical measuring section fromwould be suitable as an alternative measuring tube for the second embodiment.

102 103 103 125 107 114 121 105 105 110 114 121 121 102 102 125 107 121 103 114 121 The measuring tubehas a first antenna receptaclewhich is formed from an opening in the measuring tube wall and a hollow cylindrical collar. In the first antenna receptacle, a sealing means, a first separating disc, a resilient elementand a first disc holderare arranged. These four mentioned components serve to ensure a medium-tight boundary between the first microwave antennaand the medium to be guided. The first microwave antennais arranged in a first separating disc receptacleand extends through an opening of the resilient elementand an opening of the first disc holder. The first disc holderhas a thread and is connected to the measuring tubeor to the collar of the measuring tubevia a screw connection. The sealing meansand the first separating discare clamped between the first disc holderand a projection of the first antenna receptacle. The resilient elementin the form of a disc spring absorbs the force generated by the first disc holder.

105 5 130 131 132 133 134 133 105 103 110 128 105 128 105 3 FIG. The first microwave antennais identical to the first microwave antennaofand accordingly also has a carrier bodywith a carrier body receptaclein which a ceramic, which has an opening, is arranged. A coaxial connectoris inserted through the openingand is connected to the measuring circuit, in particular to the high-frequency generator. The first microwave antennais mounted in the first antenna receptacleand the first separating disc receptaclevia a first disc mount. The first microwave antennahas a metallic outer surface. The first disc fasteneris made of metal and covers at least part of the rear side of the first microwave antenna.

101 When using two structurally identical microwave antennas or modules, the measuring assemblyhas two of the shown assemblies.

6 FIG. 1 1 1 9 9 9 9 shows a perspective and partially cutaway view of the measuring assemblyaccording to the invention. The measuring assemblycomprises a measuring sensor which is designed to couple a received excitation signal into a medium to be examined and to measure a measuring signal which correlates with the property of the medium to be examined. Furthermore, the measuring assemblycomprises a measuring transducer which is designed to provide an excitation signal, to evaluate the measured measuring signal, and to determine the property to be determined. For this purpose, the measuring transducer has a measurement circuitwhich has a high-frequency generator for supplying the first microwave antenna with an excitation signal, in particular with a sequence of high-frequency signals. Furthermore, the measurement circuitis configured to determine the property of the medium on the basis of a received measuring signal. For the determination, the measurement circuithas a microprocessor, a memory and logical switching components. Furthermore, a computer program product which has the algorithm for determining the property of the medium can be stored in the measurement circuit.

1 2 16 17 16 3 16 16 20 5 20 20 2 1 35 1 2 1 2 2 1 1 FIG. The measuring assemblyfurther comprises an in particular a metallic measuring tubewhich has a first measuring tube sectionwith a first outer diameter Dand a second measuring tube sectionwith a second outer diameter D. The first outer diameter Dlarger than the second outer diameter Dand increases—starting from the second outer diameter D—continuously in the longitudinal direction of the measuring tube until it reaches a maximum outer diameter. After that, the first outer diameter decreases D. This results in a widening of the measuring tube in the first measuring tube section. The first antenna receptacleis arranged in a first measuring tube section. A part of the first measuring tube sectionis the measuring section. The first microwave antennais arranged in the measuring section. The measuring sectionis designed spherical in the depicted embodiment. For example, a VARINLINE® housing from GEA which is designed without dead space is suitable as measuring tubeand is therefore ideal for hygienic applications. Furthermore, the measuring assemblycomprises a housingwhich encloses the individual components of the module fromor the microwave antenna and protects them against external influences.

1 101 Measuring assembly, 2 102 Measuring tube, 3 First antenna receptacle 4 Second antenna receptacle 5 105 First microwave antenna, 6 106 Second microwave antenna, 7 107 First separating disc, 8 108 Second separating disc, 9 Measurement circuit 10 110 First separating disc receptacle, 12 First separating disc section 13 Second separating disk section 114 Elastic element 15 Measuring tube collar 16 First measuring tube section 17 Second measuring tube section 19 Fastening means 20 Measuring section 21 121 First disc holder, 22 122 Second disc holder, 23 Front section 24 Sealing means receptacle 25 125 Sealing means, 26 Measuring tube interior 27 127 Fastening means, 28 128 First disc fastener, 29 129 Second disc fastener, 30 130 Carrier body, 31 131 Carrier body receptacle, 32 132 Ceramic, 33 133 Opening, 34 134 Coaxial connector, 35 Housing